1. Field of the Invention
The present invention relates to a ceramics composite member and method of producing the same.
2. Description of the Related Art
Structural ceramics are used as heat-resistant members and abrasion-resistant members because they excel in environment resistance, heat resistance and abrasion resistance and also have outstanding characteristics such as high rigidity, low thermal expansion and low specific gravity. Ceramic members such as alumina (Al2O3), zirconia (ZrO2), silicon nitride (Si3N4) and silicon carbide (SiC) are being worked mainly toward practical use for semiconductor-related components such as jigs for semiconductor production equipment and others in these years. Besides, the ceramic members are being applied to industrial equipment such as nuclear, gas turbine and other energy equipment parts, structural parts for space, automobile engine parts, heat exchanger parts, pump parts, mechanical seal parts, bearing parts, sliding parts and the like.
The ceramic members are known that they are hardly produced into large parts and complex-shaped parts because they generally shrink by about 20% at the time of sintering. Then, it is attempted to produce large parts and complex-shaped parts by bonding plural ceramic members. As a method of bonding the ceramic members, there are known, for example, a method of bonding them with a brazing material containing active metal and a method of bonding the ceramic members with a brazing material after metallizing their surfaces. But, such bonding methods have a disadvantage that the heat resistance and strength of the parts are limited depending on a metal layer which is present as a bonding layer.
In contrast to the bonding method using the brazing material, there is known a method of bonding plural ceramic members by utilizing reaction sintering of silicon carbide. Japanese Patent Publication No. HEI 5-079630 (KOKOKU) describes a method of bonding a silicon carbide body and a porous body of silicon carbide with an organic binder containing silicon carbide particles. The silicon carbide body and the porous body of silicon carbide are overlaid with the organic binder containing the silicon carbide particles therebetween, and they are impregnated with silicon melted from the top surface of the porous body of silicon carbide. The melted silicon impregnated through the pores in the porous body of silicon carbide and the carbon in the organic binder are reacted to produce the silicon carbide layer (bonding layer) so as to join the silicon carbide body and the porous body of silicon carbide.
But, the conventional bonding method using the reaction sintering of silicon carbide has a disadvantage that applicable component shapes are limited because the melted silicon impregnates through the pores in the porous body of silicon carbide. It also has a disadvantage that the strength of the bonded body cannot be enhanced sufficiently because the process of producing the silicon carbide in the bonding layer cannot be controlled. For example, the reaction-sintering layer as the bonding layer has a microheterogeneous structure, and many pores and coarse free silicon phases are produced in the reaction-sintering layer. They are causes to degrade the strength of the bonded body.
Pamphlet of (PCT) International Publication No. WO-A1 2004/007401 and JP-A 2005-022905 (KOKAI) describe a method of bonding plural component units including a silicon-silicon carbide composite sintered body via a reaction-sintering layer (silicon-silicon carbide composite material layer). Here, plural silicon-silicon carbide composite sintered bodies (or shaped bodies containing silicon carbide and carbon) are adhered with an organic adhesive, and the bonded portion effected with the organic adhesive is impregnated with melted silicon. And, plural component units are bonded with the bonding layer which is mainly composed of silicon carbide particles which are produced by reacting the carbon in the organic adhesive with the melted silicon and a free silicon phase present among them.
The bonding method using the organic adhesive can improve denseness of the bonding layer, controllability of the microstructure and the like because the free silicon phase is present in a network form in the interstices of the silicon carbide particles configuring the bonding layer. Thus, it becomes possible to enhance bonding strength in comparison with the method of impregnating with the melted silicon through the pores in the porous body of silicon carbide. But, the generation of the silicon carbide particles configuring the bonding layer based on only the carbon in the organic adhesive has a drawback that it is poor in reproducibility of bonding strength.
In other words, the carbon in the organic adhesive involves volume expansion when it reacts with the melted silicon, and the silicon carbide particles produced originating from the initial resin structure tend to aggregate. Therefore, the interstices of the silicon carbide particles tend to become heterogeneous, and there is a possibility that the free silicon phase segregates. The free silicon phase has less strength in comparison with the silicon carbide particles, and if the free silicon phase segregates, the bonding layer tends to have variable strength. Thus, it is a cause of lowering of the reproducibility of the bonding strength of a bonded part applying the bonding method using the organic adhesive.